CN112417680A - Steam generator secondary loop working medium mass gas content distribution estimation method and system - Google Patents

Abstract

The invention provides a method and a system for estimating mass gas content distribution of a working medium in a secondary loop of a steam generator, which are used for acquiring real-time operation data of the steam generator; establishing a descending channel model to obtain the flow, the temperature and the pressure of a liquid phase working medium at an outlet at the bottom of a descending channel at the current moment; calculating heat transfer coefficients between a coolant of a primary loop and the metal wall of the inverted U-shaped pipe and between the metal wall of the inverted U-shaped pipe and a working medium of a secondary loop; establishing a loop coolant model to obtain the temperature distribution of the metal wall of the inverted U-shaped pipe; and establishing a rising channel model to obtain the flow velocity, temperature and pressure distribution of the two-loop working medium along the height of the inverted U-shaped pipe, and calculating the mass gas content distribution of the two-loop working medium along the height of the inverted U-shaped pipe. The method is used for screening the false water level at the secondary side of the steam generator, improves the control of the water level safety limit, and provides support for the operation optimization and monitoring of the steam generator.

Description

Steam generator secondary loop working medium mass gas content distribution estimation method and system

Technical Field

The invention belongs to the technical field of nuclear power station operation optimization control, and particularly relates to a method and a system for estimating mass gas content distribution of a secondary loop working medium of a steam generator, and simultaneously provides a corresponding terminal and a corresponding storage medium.

Background

The steam generator is one of hub equipment of the nuclear power station, is one loop equipment, is two loop equipment, and is a link for connecting the two loops. In the nuclear reactor, heat generated by nuclear fission is taken out by a primary loop coolant, and is transferred to a secondary loop working medium through a U-shaped tube of a steam generator, so that water in a supercooled state is converted into saturated steam. The saturated steam flows into a steam turbine to do work, and is converted into electric energy through a coaxial generator.

The internal structure of the steam generator is very complex, and 4474 inverted U-shaped pipes, a primary rotary vane type steam-water separator and a secondary steam dryer are arranged in the steam generator. There is a complicated heat transfer process inside the steam generator. For example, on the side of the second loop of the steam generator, the heat transfer from the inverted U-shaped tube to the working fluid includes single-phase convective heat transfer, sub-cooled boiling and saturated boiling convective heat transfer. In the boiling convection heat exchange process, the working medium in the two loops is locally vaporized to form gas-liquid two-phase flow. The process of bubble generation, growth and detachment from the wall surface area strongly disturbs the water level and the heat transfer resistance of the two-circuit. And on the side of a return circuit of the steam generator, the heat transfer of the coolant to the inverted U-shaped pipe is single-phase convection heat transfer. Due to the nonlinearity, asymmetry, time lag and complexity of the two-phase flow heat exchange process of the steam generator system, at present, related researches at home and abroad mainly aim at modeling lumped parameters and simulating steady-state performance of the steam generator, and few dynamic researches on working media in the steam generator are carried out, so the research results cannot be used for improving the structural design and the operation optimization of the steam generator, and the improvement of the control quality of a real-time liquid level control system of the steam generator is not facilitated.

After searching the prior art, the invention discloses a method for establishing a full three-dimensional coupling model of a U-shaped tubular steam generator of a reactor, which is a Chinese patent with an authorized publication number of CN110020476B and an authorized publication date of 26.06.2020, and the method comprises the steps of geometric model simplification of a tube bundle region, calculation node division of tube side and shell side calculation domains, tube side energy source item processing, shell side energy source item processing, energy data exchange processing of the same coordinate positions of a tube shell and a secondary side through tube wall coupling parts, energy data exchange between nodes of the primary side and the secondary side and surrounding nodes and mutual iteration processes of the energy source items. The main contribution of the patent lies in providing a full three-dimensional coupling modeling method for a steam generator, but does not provide a calculation method for mass gas content distribution of a secondary loop working medium of the steam generator.

In conclusion, the existing published reports do not relate to the problem of estimating the mass gas content distribution of the working medium of the secondary loop of the steam generator, and the vacancy needs to be filled.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a method and a system for estimating the mass gas content distribution of a secondary loop working medium of a steam generator, and also provides a corresponding terminal and a storage medium.

The invention is realized by the following technical scheme.

According to one aspect of the invention, a method for estimating the mass gas content distribution of a working medium in a secondary loop of a steam generator is provided, wherein the steam generator is divided into a hot section, a cold section and a steam-water separator, and the method comprises the following steps:

acquiring real-time operation data of the steam generator at a given moment;

respectively establishing descending channel models of a hot section and a cold section by using the acquired real-time operation data of the steam generator to obtain the temperature, the pressure and the mass flow of the liquid phase working medium at the bottom outlet of the descending channel at the current moment;

calculating a heat transfer coefficient between a primary loop coolant and the metal wall of the inverted U-shaped pipe and a heat transfer coefficient between the metal wall of the inverted U-shaped pipe and a secondary loop working medium by using the acquired real-time operation data of the steam generator, wherein the heat transfer coefficients between the primary loop coolant and the metal wall of the inverted U-shaped pipe, between the metal wall of the inverted U-shaped pipe at the preheating section and the secondary loop working medium are calculated by adopting a Dives-Bell formula, and the heat transfer coefficients between the metal wall of the inverted U-shaped pipe at the boiling section and the secondary loop working medium are calculated by adopting a Chen formula;

respectively establishing a primary loop coolant model of a hot section and a primary loop coolant model of a cold section by using the acquired real-time operation data of the steam generator and the acquired heat transfer coefficient between the primary loop coolant and the inverted U-shaped tube metal wall to acquire the temperature distribution of the inverted U-shaped tube metal wall;

and respectively establishing rising channel models of the hot section and the cold section by using the acquired real-time operation data of the steam generator, the heat transfer coefficient between the inverted U-shaped tube metal wall and the two-loop working medium, the temperature distribution of the inverted U-shaped tube metal wall and the temperature, the pressure and the mass flow of the liquid-phase working medium at the outlet of the bottom of the descending channel, obtaining the flow velocity, the temperature and the pressure distribution of the two-loop working medium along the height of the inverted U-shaped tube at the current moment by using the temperature, the pressure and the mass flow of the liquid-phase working medium at the outlet of the bottom of the descending channel as input, and further calculating the mass gas content distribution of the two-loop working medium along the height.

Further, the method further comprises: and establishing a steam-water separator model by using the acquired real-time operation data of the steam generator and the flow speed, temperature and pressure of the gas-liquid mixture working medium at the outlet of the top of the ascending channel, and calculating to obtain the temperature, pressure and mass flow of the gas-phase working medium and the liquid-phase working medium at the outlet of the steam-water separator, wherein the liquid-phase working medium at the outlet of the steam-water separator is the inlet recirculation water of the descending channel model.

According to another aspect of the present invention, there is provided a steam generator secondary circuit working medium mass gas content distribution estimation system, comprising:

the data acquisition module is used for acquiring real-time operation data of the steam generator at a given moment;

the descending channel model module is used for establishing a descending channel model by utilizing the acquired real-time operation data of the steam generator to obtain the temperature, the pressure and the mass flow of the liquid phase working medium at the bottom outlet of the descending channel at the current moment;

the heat transfer coefficient calculation module is used for calculating the heat transfer coefficient between the coolant of the primary loop and the metal wall of the inverted U-shaped pipe and the heat transfer coefficient between the metal wall of the inverted U-shaped pipe and the working medium of the secondary loop by using the acquired real-time operation data of the steam generator;

a loop coolant model module, which establishes a loop coolant model by using the acquired real-time operation data of the related measuring points of the steam generator and the acquired heat transfer coefficient between the loop coolant and the inverted U-shaped tube metal wall to acquire the temperature distribution of the inverted U-shaped tube metal wall;

the ascending channel model module is used for establishing an ascending channel model by utilizing the acquired real-time operation data of the steam generator, the heat transfer coefficient between the metal wall of the inverted U-shaped pipe and the two-loop working medium, the temperature distribution of the metal wall of the inverted U-shaped pipe and the temperature, the pressure and the mass flow of the liquid-phase working medium at the outlet of the bottom of the descending channel, and obtaining the flow velocity, the temperature and the pressure distribution of the two-loop working medium along the height of the inverted U-shaped pipe at the current moment by utilizing the temperature, the pressure and the mass flow of the liquid-phase working medium at the outlet of the bottom of the descending channel as input, so as to calculate the mass gas content distribution of the two-loop;

and the steam-water separator model module is used for establishing a steam-water separator model by utilizing the acquired real-time operation data of the steam generator and the flow velocity, temperature and pressure of the gas-liquid mixture working medium at the outlet of the top of the ascending channel, and calculating the temperature, pressure and mass flow of the gas-phase working medium and the liquid-phase working medium at the outlet of the steam-water separator.

Compared with the prior art, the embodiment of the invention has at least one of the following beneficial effects:

the method and the system for estimating the mass gas content distribution of the working medium in the secondary loop of the steam generator, the corresponding terminal and the corresponding storage medium provided by the invention realize the real-time estimation of the mass gas content distribution of the steam generator under all working conditions, can be used for screening the false water level at the secondary side of the steam generator, improve the control of the water level safety limit, provide support conditions for the operation optimization and monitoring of the steam generator and contribute to improving the safety and the economical efficiency of the operation of a nuclear power station.

The method and the system for estimating the mass gas content distribution of the working medium in the two loops of the steam generator, and the corresponding terminal and the storage medium can describe the dynamic change process of the thermal hydraulic characteristics of the working medium in the two loops of the steam generator, thereby estimating the average mass gas content of the working medium in the ascending channel of the two loops, and being further applied to the improvement of the false water level discrimination and the liquid level safety limit control strategy.

The method and the system for estimating the mass gas content distribution of the working medium in the secondary loop of the steam generator, and the corresponding terminal and the corresponding storage medium can be used for discriminating the false water level at the secondary side of the steam generator, improving the control of the water level safety limit and providing support conditions for the operation optimization and monitoring of the steam generator.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a flow chart of a method for real-time estimation of mass gas fraction distribution in a steam generator according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a method for estimating mass-gas content distribution of a steam generator in real time according to a preferred embodiment of the present invention;

FIG. 3 is a simplified schematic diagram of a steam generator according to a preferred embodiment of the present invention;

FIG. 4 is a diagram illustrating the variation of the output load of the nuclear power plant unit according to a preferred embodiment of the present invention;

FIG. 5 is a calculation result of mass gas fraction distribution in the hot zone according to a preferred embodiment of the present invention;

FIG. 6 is a calculation result of mass gas content distribution in the cold stage according to a preferred embodiment of the present invention;

FIG. 7 is a schematic diagram of a system component for real-time estimation of mass gas fraction distribution of a steam generator according to an embodiment of the present invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

FIG. 1 is a flow chart of a method for estimating mass-gas content distribution of a secondary circuit working medium of a steam generator according to an embodiment of the present invention.

As shown in fig. 1, the method for estimating mass-gas content distribution of the working medium in the secondary circuit of the steam generator according to the embodiment may include the following steps:

s100, acquiring real-time operation data of the steam generator at a given moment;

s200, establishing a descending channel model by using the acquired real-time operation data of the steam generator to obtain the temperature, the pressure and the mass flow of the liquid phase working medium at the bottom outlet of the descending channel at the current moment;

s300, calculating a heat transfer coefficient between a primary loop coolant and the metal wall of the inverted U-shaped pipe and a heat transfer coefficient between the metal wall of the inverted U-shaped pipe and a secondary loop working medium by using the acquired real-time operation data of the steam generator;

s400, establishing a loop coolant model by using the acquired real-time operation data of the steam generator and the acquired heat transfer coefficient between the loop coolant and the inverted U-shaped tube metal wall to acquire the temperature distribution of the inverted U-shaped tube metal wall;

s500, establishing a rising channel model by utilizing the acquired real-time operation data of the steam generator, the obtained heat transfer coefficient between the inverted U-shaped tube metal wall and the two-loop working medium, the obtained temperature distribution of the inverted U-shaped tube metal wall and the obtained temperature, pressure and mass flow of the descending channel bottom outlet liquid phase working medium, obtaining the flow velocity, temperature and pressure distribution of the two-loop working medium along the height of the inverted U-shaped tube at the current moment by utilizing the obtained temperature, pressure and mass flow of the descending channel bottom outlet liquid phase working medium as input, and further calculating the mass gas content distribution of the two-loop working medium along the height of the inverted U-shaped tube at the current moment.

In a specific example of this embodiment, the real-time operation data of the relevant measuring points of the steam generator at a given moment preferably comprises:

-unit load;

-feed water temperature, pressure and mass flow;

-saturated steam temperature, pressure and mass flow;

-primary circuit coolant inlet and outlet temperature, pressure and mass flow;

-water level height.

The flow velocity, the temperature and the pressure of the gas-liquid mixture working medium at the outlet of the top of the ascending channel are obtained by resolving an ascending channel model. The algorithm can be implemented by using the prior art, such as the Runge Kutta method and the like.

FIG. 2 is a schematic diagram of the method for estimating the mass-gas content distribution of the working medium in the secondary circuit of the steam generator according to the preferred embodiment of the present invention.

As shown in fig. 2, the method for estimating mass-gas content distribution of working medium in secondary loop of steam generator according to the preferred embodiment may include the following steps:

acquiring real-time operation data of relevant measuring points of a steam generator at a given moment;

establishing a descending channel model by using the acquired real-time operation data of the related measuring points of the steam generator to obtain the temperature, the pressure and the mass flow of the liquid phase working medium at the bottom outlet of the descending channel at the current moment;

calculating the heat transfer coefficient between the primary loop coolant and the metal wall of the inverted U-shaped pipe and the heat transfer coefficient between the metal wall of the inverted U-shaped pipe and the secondary loop working medium by using the acquired real-time operation data of the related measuring points of the steam generator;

establishing a loop coolant model by utilizing the acquired real-time operation data of the related measuring points of the steam generator and the acquired heat transfer coefficient between the loop coolant and the inverted U-shaped tube metal wall to acquire the temperature distribution of the inverted U-shaped tube metal wall;

step five, establishing a rising channel model by utilizing the acquired real-time operation data of the related measuring points of the steam generator, the obtained heat transfer coefficient between the metal wall of the inverted U-shaped pipe and the two-loop working medium, the obtained temperature distribution of the metal wall of the inverted U-shaped pipe and the obtained flow, temperature and pressure of the liquid-phase working medium at the bottom outlet of the descending channel, and obtaining the flow velocity, temperature and pressure distribution of the two-loop working medium along the height of the inverted U-shaped pipe at the current moment by utilizing the temperature, pressure and mass flow of the liquid-phase working medium at the bottom outlet of the descending channel as input, so as to further calculate the mass gas content distribution of the two-loop working medium along the height of;

and step six, establishing a steam-water separator model by utilizing the acquired real-time operation data of the related measuring points of the steam generator and the flow speed, temperature and pressure of the gas-liquid mixture working medium at the outlet of the top of the ascending channel obtained by calculating the ascending channel model from bottom to top, and calculating to obtain the temperature, pressure and mass flow of the gas-phase working medium and the liquid-phase working medium at the outlet of the steam-water separator, wherein the liquid-phase working medium is recycled water.

As a preferred embodiment, the method provided by this preferred embodiment may further include, before or after step one, the following steps:

step zero, dividing the steam generator into a hot section, a cold section and a steam-water separator, wherein the hot section and the cold section are divided into a descending channel and an ascending channel respectively: the descending channel refers to a space between the shell and the inner sleeve through which the working medium flows, and the working medium flows downwards; the ascending channel is a space through which working media flow between the inner sleeve and the wall of the inverted U-shaped pipe, and the working media flow upwards.

As a preferred embodiment, in step one, obtaining operation data at a given time from a real-time database of a Distributed Control System (DCS) on site of an operating unit includes: the unit load; feed water temperature, pressure, mass flow; saturated steam temperature, pressure, mass flow; inlet and outlet temperature, pressure, mass flow rate, water level height and the like of the primary loop coolant.

As a preferred embodiment, in the second step, a descending channel model is established by using the acquired real-time operation data of the relevant measuring points of the steam generator according to the conservation relation of the mass, the energy and the momentum of the working medium, so as to obtain the temperature, the pressure and the mass flow of the liquid-phase working medium at the bottom outlet of the descending channel at the current moment.

In step zero, the rising channel of the steam generator is divided into a preheating zone and a boiling zone according to the state of the two-circuit working medium. The division of the preheating zone and the boiling zone separation interface is based on:

h_RC(t,z)＝h_sw(t,z) (1)

in the formula, h_RC(t, z) is the specific enthalpy of the two-loop working medium at the current moment t and the height z of the ascending channel, kJ/kg; h is_swAnd (t, z) is the specific enthalpy of the saturated state of the two-circuit working medium at the current moment t and the height z, kJ/kg.

As a preferred embodiment, in the second step, the ratio of the liquid-phase working medium at the inlet of the descending channel is

The feed water of (1) flows into the hot section

The feed water flows into the cold section in proportion

The recycled water flows into the hot section in proportion

The recirculating water of (a) flows into the cold section.

As a preferred embodiment of the method according to the invention,

the value range is as follows: 70-90;

the value range is as follows: 40-60.

Respectively establishing a hot section descending channel model and a cold section descending channel model of the steam generator according to the momentum, mass and energy conservation relation;

wherein, the establishment of the hot section descending channel model is shown in formulas (2) to (4):

in the formula, M_HL,DCThe mass of the hot section descending channel liquid phase working medium is kg; rho_HL,DCThe density of the liquid phase working medium at the bottom outlet of the descending channel of the hot section is kg/m³；A_HL,DCIs the cross-sectional area of the descending path of the hot leg, m²(ii) a H is the water level height of the descending channel, m; g_fwIs the mass flow of the feed water, kg/s; g_rwIs the mass flow of the recirculated water, kg/s; g_HL,DC,outThe mass flow of the liquid phase working medium at the bottom outlet of the hot section descending channel is kg/s; c_P,HL,DCThe constant-pressure specific heat capacity of a liquid phase working medium of a hot section descending channel is kJ/(kg.K); t is_HL,DCThe temperature of a liquid phase working medium at an outlet at the bottom of a hot section descending channel is K; h is_HL,DCThe specific enthalpy, kJ/kg, of the liquid-phase working medium in the hot section descending channel is measured by a working medium physical property parameter database according to the temperature and the pressure of the liquid-phase working medium in the hot section descending channelCalculating to obtain; h is_fwThe specific enthalpy of the feed water, kJ/kg, is calculated through a working medium physical property parameter database according to the feed water temperature and pressure; h is_rwThe specific enthalpy of the recirculated water, kJ/kg, is calculated through a working medium physical property parameter database according to the temperature and the pressure of the recirculated water; h is_HL,DC，outSpecific enthalpy, kJ/kg, of the liquid-phase working medium at the bottom outlet of the hot section descending channel is calculated through a working medium physical property parameter database according to the temperature and the pressure of the liquid-phase working medium at the bottom outlet of the hot section descending channel; p_HL,DCThe pressure of the liquid phase working medium at the bottom outlet of the hot section descending channel is MPa; g_HL,DCThe mass flow of the liquid phase working medium in the hot section descending channel is kg/s; f. of_HL,DCIs the hot section descent passage friction factor; d_e,HL,DCIs the equivalent diameter of the descending channel of the hot section, m; g is the acceleration of gravity, m/s²；

Obtaining the temperature, the pressure and the mass flow of the liquid phase working medium at the bottom outlet of the hot section descending channel at the current moment by solving the hot section descending channel model;

establishing a cold section descending channel model as shown in formulas (5) to (7):

in the formula, M_CL,DCIs the mass of the liquid phase working medium of the cold section descending channel, kg; rho_CL,DCIs the density of the liquid phase working medium in the descending passage of the cold section, kg/m³；A_CL,DCIs the cross-sectional area of the descending passage of the cold section, m²；G_CL,DC,outThe mass flow of the liquid phase working medium at the outlet at the bottom of the descending channel of the cold section is kg/s; c_P,CL,DCThe constant-pressure specific heat capacity of a liquid phase working medium of a descending channel of the cold section is kJ/(kg.K); t is_CL,DCIs a cold section descentTemperature of channel liquid phase working medium, K; h is_CL,DCSpecific enthalpy, kJ/kg, of the liquid-phase working medium of the cold section descending channel is calculated through a working medium physical property parameter database according to the temperature and the pressure of the liquid-phase working medium of the cold section descending channel; h is_CL,DC,outSpecific enthalpy, kJ/kg, of the liquid-phase working medium at the outlet of the bottom of the cold section descending channel is calculated through a working medium physical property parameter database according to the temperature and the pressure of the liquid-phase working medium at the outlet of the bottom of the cold section descending channel; p_CL,DCThe pressure of the liquid phase working medium in the cold section descending channel is MPa; g_CL,DCThe mass flow of the liquid phase working medium in the cold section descending channel is kg/s; f. of_CL,DCIs the friction factor of the descending passage of the cold section; d_e,CL,DCIs the equivalent diameter of the descending channel of the cold section, m;

and solving the model of the cold section descending passage to obtain the temperature, pressure and mass flow of the liquid phase working medium at the outlet at the bottom of the cold section descending passage at the current moment.

In the third step, the heat transfer coefficient between the primary loop coolant and the metal wall of the inverted U-shaped tube and the heat transfer coefficient between the metal wall of the inverted U-shaped tube and the working fluid of the secondary loop are calculated by using the acquired real-time operation data of the steam generator.

Heat transfer coefficient K between primary loop coolant of hot section and cold section and metal wall of inverted U-shaped tube_HL,PSAnd K_CL,PSAnd the heat transfer coefficient K between the metal wall of the inverted U-shaped tube in the preheating areas of the hot section and the cold section and the working medium of the two loops_HL,RC,PRAnd K_CL,RC,PRUniformly expressed as K, and calculated by adopting a Ditus-Beltt formula:

K＝0.023Re_w ^0.8Pr_w ^0.3λ_w/d_HL,MT (8)

in the formula, Re_wReynolds numbers of working media of a primary loop or a secondary loop of the corresponding hot section or cold section; pr (Pr) of_wCorresponding hot section or cold section primary loop or secondary loop working medium Plantt number; lambda [ alpha ]_wThe heat conductivity of the working medium of the primary loop or the secondary loop of the corresponding hot section or the cold section; d_HL,MTIs the inner diameter of an inverted U-shaped pipe;

heat transfer coefficient K between the metal wall of the inverted U-shaped tube and the working medium of the two loops in the boiling areas of the hot section and the cold section_*,RC,BRBy usingFormula (9) to (14) Chen formula calculation, wherein K in the hot zone_*,RC,BRIs represented by K_HL,RC,BRIn the cold stage K_*,RC,BRIs represented by K_CL,RC,BR：

K_*,RC,BR＝K_cht+K_bht (9)

In the formula, K_cht、K_bhtThe heat transfer coefficient of the convection heat transfer part and the heat transfer coefficient of the nucleate boiling heat transfer part are respectively; c_P,wIs the specific heat capacity of working medium at constant pressure; h is_fsIs the latent heat of vaporization of liquid phase working medium in a boiling region; surface tension coefficient of liquid phase working medium in the sigma boiling zone; delta T_MTThe superheat degree of the metal wall of the inverted U-shaped pipe in the boiling region is shown; delta P_MTIs the boiling zone saturated steam pressure difference; x is mass gas fraction; rho_wIs the density of the liquid phase working medium of the ascending channel; rho_sIs the ascending channel saturated vapor density; mu.s_wIs the viscosity coefficient of the liquid phase working medium of the ascending channel; mu.s_sIs the rising channel saturated steam viscosity coefficient; d_HL,MTThe inner diameter of the inverted U-shaped pipe of the hot section; g is the working medium mass flow; x_ttAnd S is an intermediate variable.

As a preferred embodiment, in step four, a loop coolant model is established by using the acquired real-time operation data of the steam generator according to the conservation relation of mass, energy and momentum of the working medium, and a loop coolant model of a hot loop and a loop coolant model of a cold loop of the steam generator are respectively established;

wherein the content of the first and second substances,

establishing a coolant model of a hot-section primary circuit as shown in formulas (15) to (18):

in the formula, ρ_HL,PSIs the density of coolant in kg/m in the primary loop of the hot section³；W_HL,PSThe flow velocity of the coolant in the first loop of the hot section is m/s; c_P,HL,PSThe constant-pressure specific heat capacity of the coolant in the hot-section primary circuit is kJ/(kg.K); t is_HL,PSIs the temperature of the coolant in the primary loop of the hot section, K; k_HL,PSThe heat transfer coefficient of the primary loop coolant of the heat section to the secondary loop working medium through the metal wall of the inverted U-shaped tube is kW/(m)²·K)；d_HL,MTThe inner diameter of the inverted U-shaped pipe of the hot section is m; p_HL,PSThe pressure of a coolant in a loop of a hot section is MPa;

solving a coolant model of a loop of the hot section to obtain the temperature distribution of the metal wall of the inverted U-shaped pipe of the hot section;

establishing a cooling agent model of a cold-stage loop as shown in formulas (19) to (22):

in the formula, ρ_CL,PSIs the density of coolant in kg/m in the primary loop of the cold stage³；W_CL,PSThe flow velocity of the coolant in the primary loop of the cold section is m/s; c_P,CL,PSThe constant-pressure specific heat capacity of the coolant in the cold-stage primary circuit is kJ/(kg.K); t is_CL,PSIs the coolant temperature of the primary loop of the cold section, K; k_CL,PSThe heat transfer coefficient of the primary loop coolant of the cold section to the secondary loop working medium through the metal wall of the inverted U-shaped tube is kW/(m)²·K)；d_CL,MTThe inner diameter of the inverted U-shaped pipe of the cold section is m; p_CL,PSThe pressure of coolant in a primary loop of the cold section is MPa;

and solving a coolant model of the primary loop of the cold section to obtain the temperature distribution of the metal wall of the inverted U-shaped pipe of the cold section.

As a preferred embodiment, in the fifth step, by using the obtained real-time operation data of the steam generator and the obtained flow, temperature and pressure of the liquid-phase working medium at the bottom outlet of the descending channel and combining the mass, energy and momentum conservation relation of the working medium, a hot section ascending channel model and a cold section ascending channel model of the steam generator are respectively established;

wherein:

establishing a hot section ascending channel model as shown in formulas (23) to (30):

in the formula, ρ_HL,RCIs the density of working medium in the rising channel of the hot section, kg/m³；W_HL,RCThe flow velocity of working medium in the ascending channel of the hot section is m/s; rho_HL,MTIs the metal wall density of the inverted U-shaped pipe of the hot section in kg/m³；C_P,HL,MTThe constant pressure specific heat capacity of the metal wall of the inverted U-shaped pipe of the hot section is kJ/(kg.K); t is_HL,MTThe temperature of the metal wall of the inverted U-shaped pipe of the hot section is K; n is the number of the inverted U-shaped tubes; k_HL,RC,PRThe heat transfer coefficient between the working medium of the second loop of the preheating zone of the ascending channel of the heat section and the metal wall of the inverted U-shaped pipe is kW/(m)²·K)；d_HL,MTThe inner diameter of the inverted U-shaped pipe of the hot section is m; t is_HL,RC，PRThe temperature of a liquid phase working medium in a preheating area of a hot section ascending channel is K; rho_HL,RC，PRIs the density of liquid phase working medium in the preheating zone of the ascending channel of the hot section, kg/m³；C_P,HL,RC,PRThe constant-pressure specific heat capacity of a liquid phase working medium in a preheating area of a rising channel of a hot section is kJ/(kg.K); w_HL,RC，PRThe flow velocity of a liquid phase working medium in a preheating area of a rising channel of a hot section is m/s; k_HL,RC,BRThe heat transfer coefficient between the working medium of the second loop in the boiling zone of the ascending channel of the heat section and the metal wall of the inverted U-shaped pipe is kW/(m)²·K)；T_HL,RC，BRThe temperature of a gas-liquid mixed phase working medium in a boiling area of a hot section ascending channel is K; rho_HL,RC，BRIs the density of gas-liquid mixed phase working medium in the boiling zone of the ascending channel of the hot section, kg/m³；C_P,HL,RC,BRThe constant-pressure specific heat capacity of a gas-liquid mixed phase working medium in a boiling region of a rising channel of a hot section is kJ/(kg.K); w_HL,RC，BRThe flow velocity of a gas-liquid mixed phase working medium in a boiling area of a hot section ascending channel is m/s; p_HL,RC,PRThe pressure of a liquid phase working medium in a preheating area of a hot section ascending channel is MPa; g_HL,RC,PRThe mass flow of the liquid phase working medium in the preheating area of the ascending channel of the hot section is kg/s; f. of_HL,RC,PRIs a friction factor of a preheating zone of a rising channel of a hot section; d_e,HL,RC,PRThe equivalent diameter m of the preheating zone of the ascending channel of the hot section; xi_HL,RC,PRIs the local resistance coefficient of the preheating zone of the ascending channel of the hot section; p_HL,RC,BRThe pressure of a gas-liquid mixed phase working medium in a boiling area of a hot section ascending channel is MPa; g_HL,RC,BRThe mass flow of a gas-liquid mixed phase working medium in a boiling area of a hot section ascending channel is kg/s; f. of_HL,RC,BRIs a friction factor of a boiling zone of a rising channel of a hot section; d_e,HL,RC,BRIs the equivalent diameter m of the boiling zone of the ascending channel of the hot section; phi is a two-phase multiplication factor; xi_HL,RC,BRIs the local resistance coefficient of the boiling area of the ascending channel of the hot section; x is mass gas content,%; rho_wIs the density of liquid phase working medium in the ascending channel, kg/m³；ρ_sIs the saturated steam density of the ascending channel, kg/m³；μ_wIs the viscosity coefficient of the liquid phase working medium of the ascending channel; mu.s_sIs the rising channel saturated steam viscosity coefficient;

solving a rising channel model of the thermal section to obtain the flow velocity, temperature, pressure and heat transfer coefficient distribution of the two-loop working medium at the current moment of the thermal section along the height of the inverted U-shaped pipe;

establishing a cold section ascending channel model as shown in formulas (31) to (37):

in the formula, ρ_CL,RCIs the density of working medium in the ascending channel of the cold section, kg/m³；W_CL,RCThe flow velocity of working medium in the ascending channel of the cold section is m/s; rho_CL,MTIs the metal wall density of the inverted U-shaped pipe of the cold section in kg/m³；C_P,CL,MTThe constant pressure specific heat capacity of the metal wall of the inverted U-shaped pipe of the cold section is kJ/(kg.K); t is_CL,MTThe temperature of the metal wall of the inverted U-shaped pipe of the cold section is K; k_CL,RC,PRThe heat transfer coefficient between the working medium of the second loop of the preheating zone of the ascending channel of the cold section and the metal wall of the inverted U-shaped pipe is kW/(m)²·K)；d_CL,MTThe inner diameter of the inverted U-shaped pipe of the cold section is m; t is_CL,RC，PRThe temperature of a liquid phase working medium in a preheating area of a cold section ascending channel is K; rho_CL,RC，_PRThe density of liquid phase working medium in a preheating zone of an ascending channel of a cold section is kg/m³；C_P,CL,RC,PRThe constant-pressure specific heat capacity of a liquid phase working medium in a preheating area of a cold section ascending channel is kJ/(kg.K); w_CL,RC,PRThe flow velocity of liquid phase working medium in a preheating area of a cold section ascending channel is m/s; k_CL,RC,BRThe heat transfer coefficient between the working medium of the second loop of the boiling zone of the ascending channel of the cold section and the metal wall of the inverted U-shaped pipe is kW/(m)²·K)；T_CL,RC,BRThe temperature of a gas-liquid mixed phase working medium in a boiling area of a cold section ascending channel is K; rho_CL,RC,BRIs the density of gas-liquid mixed phase working medium in the boiling zone of the ascending channel of the cold section, kg/m³；C_P,CL,RC,BRThe constant-pressure specific heat capacity of a gas-liquid mixed phase working medium in a boiling region of an ascending channel of a cold section is kJ/(kg.K); w_CL,RC,BRThe flow velocity of a gas-liquid mixed phase working medium in a boiling area of a cold section ascending channel is m/s; p_CL,RC,PRIs liquid phase working in preheating zone of ascending channel of cold sectionMass pressure, MPa; g_CL,RC,PRThe mass flow of the liquid phase working medium in the preheating area of the ascending channel of the cold section is kg/s; f. of_CL,RC,PRIs the friction factor of the preheating zone of the ascending channel of the cold section; d_e,CL,RC,PRThe equivalent diameter m of the preheating zone of the ascending channel of the cold section; xi_CL,RC,PRIs the local resistance coefficient of the preheating zone of the ascending channel of the cold section; p_CL,RC,BRThe pressure of a gas-liquid mixed phase working medium in a boiling region of an ascending channel of the cold section is MPa; g_CL,RC,BRThe mass flow of a gas-liquid mixed phase working medium in a boiling area of a cold section ascending channel is kg/s; f. of_CL,RC,BRIs the friction factor of the boiling zone of the ascending channel of the cold section; d_e,CL,RC,BRThe equivalent diameter m of the boiling zone of the ascending channel of the cold section; xi_CL,RC,BRIs the local resistance coefficient of the boiling area of the ascending channel of the cold section;

and solving the rising channel model of the cold section to obtain the flow velocity, temperature, pressure and heat transfer coefficient distribution of the two-loop working medium along the height of the inverted U-shaped pipe at the current moment of the cold section.

Further, calculating the mass gas content distribution of the working medium of the two loops along the height of the inverted U-shaped pipe at the current moment:

in the formula, h_BRIs the specific enthalpy of a gas-liquid mixed phase working medium in a boiling region, kJ/kg; h is_ssIs the boiling zone saturated steam specific enthalpy, kJ/kg; h is_swIs boiling zone saturated water specific enthalpy, kJ/kg; x is the number of_BRMass gas content of the working medium in a boiling region is percent; h is_BR,h_swAnd h_swAnd calculating according to the temperature and the pressure of the gas-liquid mixed phase working medium in the boiling region through a working medium physical property parameter database.

As a preferred embodiment, in step six, the steam-water separator model is represented by formulas (39) to (46):

G_ss,SP,out＝(x_HL,RC,BR,outG_HL,RC,BR,out+x_CL,RC,BR,outG_CL,RC,BR,out)×η (39)

G_sw,SP,out＝(1-x_HL,RC,BR,out×η)G_HL,RC,BR,out+(1-x_CL,RC,BR,out×η)G_CL,RC,BR,out (40)

G_SP,in＝G_HL,RC,BR,out+G_CL,RC,BR,out (42)

P_SP,in＝P_HL,RC,BR,out＝P_CL,RC,BR,out (43)

T_SP,in＝T_HL,RC,BR,out＝T_CL,RC,BR,out (44)

P_SP,out＝P_ss,SP,out＝T_sw,SP,out (45)

T_SP,in＝T_ss,SP,out＝T_sw,SP,out (46)

in the formula, G_ss,SP,outThe mass flow of saturated steam at the outlet of the steam-water separator is kg/s; x is the number of_HL,RC,BR,outMass gas content percent of gas-liquid mixed phase working medium at an outlet of a boiling zone of a rising channel of a hot section; g_HL,RC,BR,outThe mass flow of the gas-liquid mixed phase working medium at the outlet of the boiling zone of the ascending channel of the hot section is kg/s; x is the number of_CL,RC,BR,outMass gas content percent of gas-liquid mixed phase working medium at an outlet of a boiling zone of an ascending channel of a cold section; g_CL,RC,BR,outThe mass flow of the gas-liquid mixed phase working medium at the outlet of the boiling zone of the ascending channel of the cold section is kg/s; η is the steam-water separator efficiency,%; g_sw,SP,outThe mass flow of saturated water at the outlet of the steam-water separator is kg/s; p_SP,outThe pressure of working medium at the outlet of the steam-water separator is MPa; p_ss,SP,outSaturated steam pressure at an outlet of the steam-water separator is MPa; p_sw,SP,outThe saturated water pressure at the outlet of the steam-water separator is MPa; p_SP,inThe pressure of a gas-liquid mixed phase working medium at the inlet of the steam-water separator is MPa; t is_SP,inThe temperature of a gas-liquid mixed phase working medium at the inlet of the steam-water separator is K; t is_CL,RC,BR,outThe temperature of a gas-liquid mixed phase working medium at the outlet of a boiling zone of an ascending channel of a cold section is K; t is_HL,RC,BR,outIs the outlet gas of the boiling zone of the ascending channel of the hot sectionTemperature of liquid mixed phase working medium, K; xi_SPIs the partial resistance coefficient of the steam-water separator; g_SP,inThe mass flow of gas-liquid mixed phase working medium at the inlet of the steam-water separator is kg/s; rho_SP,inIs the density of gas-liquid mixed phase working medium at the inlet of the steam-water separator, kg/m³；P_HL,RC,BR,outThe pressure of a gas-liquid mixed phase working medium at the outlet of a boiling zone of a rising channel of a hot section is MPa; p_CL,RC,BR,outThe pressure of a gas-liquid mixed phase working medium at the outlet of a boiling zone of an ascending channel of a cold section is MPa; t is_ss,SP,outIs the steam-water separator outlet saturated steam temperature, K; t is_sw,SP,outIs the saturated water temperature at the outlet of the steam-water separator, K; rho_HL,RC,BR,outThe density of gas-liquid mixed phase working medium at the outlet of the boiling zone of the ascending channel of the hot section is kg/m³；ρ_CL,RC,BR,outThe density of gas-liquid mixed phase working medium at the outlet of the boiling zone of the ascending channel of the cold section is kg/m³；

And solving the steam-water separator model to obtain the temperature, pressure and mass flow of saturated water at the outlet of the steam-water separator and saturated steam, wherein the liquid-phase working medium is recirculated water.

On the basis of the above embodiments, the method may further include step S600, in which a steam-water separator model is established by using the acquired real-time operation data of the steam generator and the flow rate, temperature, and pressure of the gas-liquid mixture working medium at the top outlet of the ascending channel, and the temperature, pressure, and mass flow of the gas-phase working medium and the liquid-phase working medium at the outlet of the steam-water separator are calculated. Wherein, the liquid phase working medium is the recirculation water, namely the recirculation water at the inlet of the descending channel model in S200.

The method for estimating mass gas content distribution of a steam generator in real time provided by the preferred embodiment includes acquiring data of load, feed water temperature, pressure, mass flow, saturated steam temperature, pressure, mass flow, primary circuit coolant inlet and outlet temperature, pressure, mass flow, water level height and the like of the unit at a given moment from a real-time measurement database of a DCS (distributed control system) on-site running the unit, resolving a hot section model, a cold section model and a steam-water separator model by combining a working medium physical property parameter database and a steam generator structure parameter database, and outputting hot section and cold section mass gas content distribution.

Fig. 3 is a simplified schematic diagram of the steam generator. According to the real structure of the steam generator, the steam generator is simplified and divided into a hot section, a cold section and a steam-water separator. The two loops of the hot section and the cold section can be divided into a preheating zone and a boiling zone according to whether the working medium reaches a saturated state or not.

In the method for estimating mass gas content distribution of the working medium in the secondary loop of the steam generator provided by the preferred embodiment, as shown in fig. 4, actual measurement data of the steam generator DCS of the nuclear power plant unit of the embodiment under different loads in 6 months and 10 days in 2019 are obtained.

FIG. 5 is a diagram showing the estimation result of mass gas content distribution of the working medium in the hot section and the second loop along the z direction, and FIG. 6 is a diagram showing the estimation result of mass gas content distribution of the working medium in the cold section and the second loop along the z direction. As can be seen from fig. 5 and 6, the mass gas content at any height z of the boiling zone increases with increasing load on the nuclear power plant unit, and vice versa.

In another embodiment of the present invention, a system for estimating mass-gas content distribution of a secondary loop working medium of a steam generator is further provided, as shown in fig. 7, the system may include: the system comprises a data acquisition module, a descending channel model module, a heat transfer coefficient calculation module, a primary loop coolant model module, an ascending channel model module and a steam-water separator model module. Wherein: the data acquisition module is used for acquiring real-time operation data of related measuring points of the steam generator at a given moment; the descending channel model module is used for establishing a descending channel model by utilizing the acquired real-time operation data of the related measuring points of the steam generator to obtain the temperature, the pressure and the mass flow of the liquid phase working medium at the bottom outlet of the descending channel at the current moment; the heat transfer coefficient calculation module is used for calculating the heat transfer coefficient between the primary loop coolant and the metal wall of the inverted U-shaped pipe and the heat transfer coefficient between the metal wall of the inverted U-shaped pipe and the secondary loop working medium by using the acquired real-time operation data of the related measuring points of the steam generator; a loop coolant model module, which establishes a loop coolant model by using the acquired real-time operation data of the related measuring points of the steam generator and the acquired heat transfer coefficient between the loop coolant and the inverted U-shaped tube metal wall to acquire the temperature distribution of the inverted U-shaped tube metal wall; and the ascending channel model module is used for establishing an ascending channel model by utilizing the acquired real-time operation data of the related measuring points of the steam generator, the obtained heat transfer coefficient between the metal wall of the inverted U-shaped pipe and the two-loop working medium, the obtained temperature distribution of the metal wall of the inverted U-shaped pipe and the obtained temperature, pressure and mass flow of the liquid-phase working medium at the bottom outlet of the descending channel, and the temperature, pressure and mass flow of the liquid-phase working medium at the bottom outlet of the descending channel are used as input to obtain the flow velocity, temperature and pressure distribution of the two-loop working medium along the height of the inverted U-shaped pipe at the current moment, so that the mass gas content distribution of the two-loop working medium along the height of the. Of course, optionally, a steam-water separator model module may be further included, and the module establishes a steam-water separator model by using the acquired real-time operation data of the relevant measuring points of the steam generator and the flow rate, temperature and pressure of the gas-liquid mixture working medium at the top outlet of the ascending channel, and calculates the temperature, pressure and mass flow of the gas-phase working medium and the liquid-phase working medium at the outlet of the steam-water separator.

The embodiment of the invention provides a method for estimating the mass gas content distribution of a working medium in a secondary loop of a steam generator, and provides a method for estimating (identifying) the mass gas content distribution of the working medium in the secondary loop of the steam generator by combining mechanical modeling and real-time measurement data of a DCS (distributed control system on site for operating a unit). And finally, calculating mass gas content distribution of the two-loop working medium in real time based on the model and DCS measurement data, wherein the mass gas content is defined as the proportion of gas phase in the total mass of the two-phase fluid flowing through a certain section in unit time.

The method and the system for estimating the mass-gas content distribution of the working medium in the secondary loop of the steam generator, as well as the corresponding terminal and the storage medium provided by the embodiment of the invention, wherein the mass-gas content of the working medium refers to the proportion of the gas phase in the total mass of the water-steam two-phase flow fluid flowing through a certain section in unit time. The embodiment of the invention obtains real-time measurement data of a related measuring point of the steam generator at a given moment; dividing a steam generator into a hot section, a cold section and a steam-water separator, wherein the hot section and the cold section are divided into a descending channel and an ascending channel: the descending channel is a space between the steam generator shell and the inner sleeve through which two loops of working medium flow, and the ascending channel is a space between the inner sleeve and the pipe wall of the inverted U-shaped pipe through which two loops of working medium flow; solving the descending channel model to obtain the specific enthalpy, flow, temperature, pressure and density of the working medium of the second loop at the outlet of the bottom of the descending channel at the current moment; solving the ascending channel model to obtain specific enthalpy, flow, temperature, pressure and density distribution of the two-loop working medium along the height of the inverted U-shaped pipe at the current moment, and further calculating mass gas content distribution of the two-loop working medium along the height of the inverted U-shaped pipe at the current moment; solving a steam-water separator model to calculate and obtain the temperature, pressure and flow of the working medium at the outlet of the steam-water separator; the dynamic change process of the thermal hydraulic characteristics of the two-loop working medium in the steam generator can be described, so that the average mass gas content of the two-loop ascending channel working medium can be estimated, and the method can be further applied to improvement of false water level discrimination and liquid level safety limit control strategies. The technical scheme provided by the embodiment of the invention realizes the real-time estimation of the mass gas content distribution of the steam generator under all working conditions, can be used for discriminating the false water level at the secondary side of the steam generator, improves the water level safety limit control, provides support conditions for the operation optimization and monitoring of the steam generator, and is beneficial to improving the safety and the economical efficiency of the operation of the nuclear power station.

It should be noted that, the steps in the method provided by the present invention may be implemented by using corresponding modules, devices, units, and the like in the system, and those skilled in the art may implement the composition of the system by referring to the technical solution of the method, that is, the embodiment in the method may be understood as a preferred example for constructing the system, and will not be described herein again.

Those skilled in the art will appreciate that, in addition to implementing the system and its various devices provided by the present invention in purely computer readable program code means, the method steps can be fully programmed to implement the same functions by implementing the system and its various devices in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system and various devices thereof provided by the present invention can be regarded as a hardware component, and the devices included in the system and various devices thereof for realizing various functions can also be regarded as structures in the hardware component; means for performing the functions may also be regarded as structures within both software modules and hardware components for performing the methods.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.

Claims (11)

1. A steam generator secondary loop working medium mass gas content distribution estimation method divides a steam generator into a hot section, a cold section and a steam-water separator, and is characterized by comprising the following steps:

acquiring real-time operation data of the steam generator at a given moment;

respectively establishing descending channel models of a hot section and a cold section by using the acquired real-time operation data of the steam generator to obtain the temperature, the pressure and the mass flow of the liquid phase working medium at the bottom outlet of the descending channel at the current moment;

calculating the heat transfer coefficient between a primary loop coolant and the metal wall of the inverted U-shaped pipe and the heat transfer coefficient between the metal wall of the inverted U-shaped pipe and a secondary loop working medium by using the acquired real-time operation data of the steam generator, wherein the heat transfer coefficients between the primary loop coolant and the metal wall of the inverted U-shaped pipe and between the metal wall of the inverted U-shaped pipe of the preheating section and the secondary loop working medium are calculated by adopting a Dives-Bell formula, and the heat transfer coefficients between the metal wall of the inverted U-shaped pipe of the boiling section and the secondary loop working medium are calculated by adopting a Chen formula;

respectively establishing a primary loop coolant model of a hot section and a primary loop coolant model of a cold section by using the acquired real-time operation data of the steam generator and the acquired heat transfer coefficient between the primary loop coolant and the inverted U-shaped tube metal wall to acquire the temperature distribution of the inverted U-shaped tube metal wall;

and respectively establishing rising channel models of the hot section and the cold section by using the acquired real-time operation data of the steam generator, the heat transfer coefficient between the inverted U-shaped tube metal wall and the two-loop working medium, the temperature distribution of the inverted U-shaped tube metal wall and the temperature, the pressure and the mass flow of the liquid-phase working medium at the outlet of the bottom of the descending channel, obtaining the flow velocity, the temperature and the pressure distribution of the two-loop working medium along the height of the inverted U-shaped tube at the current moment by using the temperature, the pressure and the mass flow of the liquid-phase working medium at the outlet of the bottom of the descending channel as input, and further calculating the mass gas content distribution of the two-loop working medium along the height.

2. The method for estimating mass-gas content distribution of a secondary loop working medium of a steam generator according to claim 1, wherein the data about real-time operation of relevant measuring points of the steam generator at a given moment comprises:

-unit load;

-feed water temperature, pressure and mass flow;

-saturated steam temperature, pressure and mass flow;

-primary circuit coolant inlet and outlet temperature, pressure and mass flow;

-water level height.

3. The method according to claim 1, wherein in the ascending channel of the steam generator, the ascending channel is divided into a preheating zone and a boiling zone according to the state of the two-loop working medium; wherein, the division of the preheating zone and the boiling zone distinguishing interface is based on the following steps:

h_RC(t,z)＝h_sw(t,z) (1)

in the formula, h_RC(t, z) is the specific enthalpy of the two-loop working medium at the current moment t and the height z of the ascending channel; h is_swAnd (t, z) is the specific enthalpy of the saturated state of the two-circuit working medium at the current moment t and the height z.

4. The method for estimating the mass gas content distribution of the working medium in the secondary loop of the steam generator according to claim 1, wherein a hot section descending channel model and a cold section descending channel model of the steam generator are respectively established according to the momentum, mass and energy conservation relation of the liquid phase working medium at the inlet of a descending channel of the steam generator in real-time operation data of the steam generator;

wherein:

the established hot section descending channel model is shown in formulas (2) to (4):

in the formula, M_HL,DCThe quality of the liquid phase working medium of the hot section descending channel; rho_HL,DCThe density of the liquid phase working medium at the bottom outlet of the hot section descending channel; a. the_HL,DCIs the cross-sectional area of the hot leg downcomer channel; h is the water level height of the descent passage; g_fwIs the feed water mass flow; g_rwIs the recirculation water mass flow; g_HL,DC,outThe mass flow of the liquid phase working medium at the bottom outlet of the hot section descending channel; c_P,HL,DCThe constant pressure specific heat capacity of the liquid phase working medium of the hot section descending channel; t is_HL,DCThe temperature of the liquid phase working medium at the bottom outlet of the hot section descending channel; h is_HL,DCThe specific enthalpy of the liquid-phase working medium of the hot section descending channel is calculated through a working medium physical property parameter database according to the temperature and the pressure of the liquid-phase working medium of the hot section descending channel; h is_fwThe specific enthalpy of the feed water is obtained by calculation through a working medium physical property parameter database according to the temperature and the pressure of the feed water; h is_rwThe specific enthalpy of the recirculated water is calculated through a working medium physical property parameter database according to the temperature and the pressure of the recirculated water; h is_HL,DC，outThe specific enthalpy of the liquid phase working medium at the bottom outlet of the heat section descending channel is determined according to the heatThe temperature and the pressure of the liquid-phase working medium at the outlet at the bottom of the section descending channel are obtained by calculation through a working medium physical property parameter database; p_HL,DCThe pressure of the liquid phase working medium at the bottom outlet of the hot section descending channel; g_HL,DCThe mass flow of the liquid phase working medium in the hot section descending channel; f. of_HL,DCIs the hot section descent passage friction factor; d_e,HL,DCIs the equivalent diameter of the descending channel of the hot section; g is the acceleration of gravity;

obtaining the temperature, the pressure and the mass flow of the liquid phase working medium at the bottom outlet of the hot section descending channel at the current moment by solving the hot section descending channel model;

the established cold section descending channel model is shown in formulas (5) to (7):

in the formula, M_CL,DCThe quality of a liquid phase working medium of a cold section descending channel; rho_CL,DCThe density of a liquid phase working medium in a descending channel of the cold section; a. the_CL,DCIs the cross-sectional area of the cold section descending channel; g_CL,DC,outMass flow of liquid phase working medium at the outlet at the bottom of the descending passage of the cold section; c_P,CL,DCThe constant pressure specific heat capacity of the liquid phase working medium of the cold section descending channel; t is_CL,DCThe temperature of the liquid phase working medium in the cold section descending channel; h is_CL,DCThe specific enthalpy of the liquid-phase working medium of the cold section descending channel is calculated through a working medium physical property parameter database according to the temperature and the pressure of the liquid-phase working medium of the cold section descending channel; h is_CL,DC,outSpecific enthalpy of a liquid-phase working medium at an outlet at the bottom of a cold section descending channel is calculated through a working medium physical property parameter database according to the temperature and pressure of the liquid-phase working medium at the outlet at the bottom of the cold section descending channel; p_CL,DCAt the cold stageReducing the pressure of the channel liquid phase working medium; g_CL,DCMass flow of liquid phase working medium in a descending channel of the cold section; f. of_CL,DCIs the friction factor of the descending passage of the cold section; d_e,CL,DCIs the equivalent diameter of a descending channel of the cold section;

and solving the model of the cold section descending passage to obtain the temperature, pressure and mass flow of the liquid phase working medium at the outlet at the bottom of the cold section descending passage at the current moment.

5. The method of claim 4, wherein the mass-gas content distribution of the steam generator secondary circuit working medium is determined by the ratio of liquid phase working medium at the inlet of the steam generator descending channel

The feed water of (1) flows into the hot section

The feed water flows into the cold section in proportion

The recycled water flows into the hot section in proportion

The recirculating water of (a) flows into the cold section.

6. The method of claim 1, wherein the heat transfer coefficient K between the primary coolant of the hot and cold stages and the metal wall of the inverted U-tube is determined by the mass-to-gas fraction distribution of the secondary loop of the steam generator_HL,PSAnd K_CL,PSAnd the heat transfer coefficient K between the metal wall of the inverted U-shaped pipe in the preheating areas of the hot section and the cold section and the working medium of the two loops_HL,RC,PRAnd K_CL,RC,PRUniformly expressed as K, and calculated by adopting a Ditus-Beltt formula as follows:

K＝0.023Re_w ^0.8Pr_w ^0.3λ_w/d_HL,MT (8)

in the formula, Re_wReynolds numbers of working media of a primary loop or a secondary loop of the corresponding hot section or cold section; pr (Pr) of_wCorresponding hot section or cold section primary loop or secondary loop working medium Plantt number; lambda [ alpha ]_wThe heat conductivity of the working medium of the primary loop or the secondary loop of the corresponding hot section or the cold section; d_HL,MTIs the inner diameter of an inverted U-shaped pipe;

the heat transfer coefficient K between the metal wall of the inverted U-shaped pipe in the boiling areas of the hot section and the cold section and the working medium of the two loops_HL,RC,BRAnd K_CL,RC,BRIs uniformly represented as K_*,RC,BRThe formula (9) to (14) Chen is used to calculate as follows:

K_*,RC,BR＝K_cht+K_bht (9)

in the formula, K_cht、K_bhtThe heat transfer coefficient of the convection heat transfer part and the heat transfer coefficient of the nucleate boiling heat transfer part are respectively; c_P,wIs the specific heat capacity of working medium at constant pressure; h is_fsIs the latent heat of vaporization of liquid phase working medium in a boiling region; surface tension coefficient of liquid phase working medium in the sigma boiling zone; delta T_MTIs a boiling zone inverted U-shaped tube metalWall superheat; delta P_MTIs the boiling zone saturated steam pressure difference; x is mass gas fraction; rho_wIs the density of the liquid phase working medium of the ascending channel; rho_sIs the ascending channel saturated vapor density; mu.s_wIs the viscosity coefficient of the liquid phase working medium of the ascending channel; mu.s_sIs the rising channel saturated steam viscosity coefficient; d_HL,MTThe inner diameter of the inverted U-shaped pipe of the hot section; g is the working medium mass flow; x_ttAnd S is an intermediate variable.

7. The method for estimating mass-gas content distribution of the working medium in the secondary loop of the steam generator according to claim 1, wherein a primary loop coolant model in the hot section and a primary loop coolant model in the cold section of the steam generator are respectively established according to real-time operation data of the steam generator and the momentum, mass and energy conservation relation of the primary loop coolant;

wherein the content of the first and second substances,

the established hot-section primary circuit coolant model is shown in formulas (15) to (18):

in the formula, ρ_HL,PSIs the hot section primary circuit coolant density; w_HL,PSIs the flow rate of the coolant in the primary loop of the hot section; c_P,HL,PSThe constant-pressure specific heat capacity of the coolant in the hot section primary circuit is shown; t is_HL,PSIs the temperature of the coolant in the primary loop of the hot section; k_HL,PSThe heat transfer coefficient of the coolant of the primary loop of the hot section transferring heat to the working medium of the secondary loop through the metal wall of the inverted U-shaped tube is shown; d_HL,MTThe inner diameter of the inverted U-shaped pipe of the hot section; p_HL,PSIs the coolant pressure of the primary loop of the hot section;

solving a coolant model of a loop of the hot section to obtain the temperature distribution of the metal wall of the inverted U-shaped pipe of the hot section;

the established cold-stage primary circuit coolant model is shown in formulas (19) to (22):

in the formula, ρ_CL,PSIs the cold stage primary circuit coolant density; w_CL,PSIs the flow rate of the coolant in the primary loop of the cold stage; c_P,CL,PSThe constant-pressure specific heat capacity of the coolant in the cold-section primary loop is determined; t is_CL,PSIs the coolant temperature of the primary loop of the cold section; k_CL,PSThe heat transfer coefficient of the coolant of the primary loop of the cold section transferring heat to the working medium of the secondary loop through the metal wall of the inverted U-shaped tube is shown; d_CL,MTThe inner diameter of the inverted U-shaped pipe of the cold section; p_CL,PSIs the coolant pressure of the primary loop of the cold section;

and solving a coolant model of the primary loop of the cold section to obtain the temperature distribution of the metal wall of the inverted U-shaped pipe of the cold section.

8. The method for estimating the mass gas content distribution of the working medium in the secondary loop of the steam generator according to claim 1, wherein a hot section ascending channel model and a cold section ascending channel model of the steam generator are respectively established according to real-time operation data of the steam generator and the momentum, mass and energy conservation relation of the working medium in the ascending channel of the steam generator;

wherein:

the established hot segment ascending channel model is shown in formulas (23) to (30):

in the formula，ρ_HL,RCIs the working medium density of the hot section ascending channel; w_HL,RCThe flow velocity of the working medium of the hot section ascending channel; rho_HL,MTThe metal wall density of the inverted U-shaped pipe of the hot section; c_P,HL,MTThe constant pressure specific heat capacity of the metal wall of the inverted U-shaped pipe of the hot section; t is_HL,MTThe temperature of the metal wall of the inverted U-shaped pipe of the hot section; n is the number of the inverted U-shaped tubes; k_HL,RC,PRThe heat transfer coefficient between the working medium of the second loop in the preheating area of the ascending channel of the hot section and the metal wall of the inverted U-shaped pipe is determined; d_HL,MTThe inner diameter of the inverted U-shaped pipe of the hot section; t is_HL,RC，PRThe temperature of the liquid phase working medium in the preheating area of the rising channel of the hot section; rho_HL,RC，PRThe density of the liquid phase working medium in the preheating area of the ascending channel of the hot section; c_P,HL,RC,PRThe constant pressure specific heat capacity of a liquid phase working medium in a preheating area of a hot section ascending channel; w_HL,RC，PRThe flow velocity of the liquid phase working medium in the preheating area of the ascending channel of the hot section; k_HL,RC,BRThe heat transfer coefficient between the working medium of the second loop in the boiling area of the ascending channel of the hot section and the metal wall of the inverted U-shaped pipe is determined; t is_HL,RC，BRThe temperature of a gas-liquid mixed phase working medium in a boiling area of a hot section ascending channel; rho_HL,RC，BRThe density of a gas-liquid mixed phase working medium in a boiling area of a hot section ascending channel; c_P,HL,RC,BRThe constant pressure specific heat capacity of a gas-liquid mixed phase working medium in a boiling region of a hot section ascending channel; w_HL,RC，BRThe flow velocity of a gas-liquid mixed phase working medium in a boiling region of a hot section ascending channel; p_HL,RC,PRThe pressure a of the liquid phase working medium in the preheating area of the rising channel of the hot section is shown; g_HL,RC,PRMass flow of liquid phase working medium in a preheating area of a hot section ascending channel; f. of_HL,RC,PRIs a friction factor of a preheating zone of a rising channel of a hot section; d_e,HL,RC,PRThe equivalent diameter of a preheating zone of a rising channel of a hot section; xi_HL,RC,PRIs the local resistance coefficient of the preheating zone of the ascending channel of the hot section; p_HL,RC,BRThe pressure of a gas-liquid mixed phase working medium in a boiling area of a hot section ascending channel; g_HL,RC,BRThe mass flow of the working medium of the gas-liquid mixed phase in the boiling area of the ascending channel of the hot section; f. of_HL,RC,BRIs a friction factor of a boiling zone of a rising channel of a hot section; d_e,HL,RC,BRIs the equivalent diameter of the boiling zone of the ascending channel of the hot section; phi is a two-phase multiplication factor; xi_HL,RC,BRIs the local resistance coefficient of the boiling area of the ascending channel of the hot section; x is mass gas fraction; rho_wIs the density of the liquid phase working medium of the ascending channel; rho_sIs the ascending channel saturated vapor density; mu.s_wIs the viscosity coefficient of the liquid phase working medium of the ascending channel; mu.s_sIs the rising channel saturated steam viscosity coefficient;

solving a rising channel model of the thermal section to obtain the flow velocity, temperature, pressure and heat transfer coefficient distribution of the two-loop working medium at the current moment of the thermal section along the height of the inverted U-shaped pipe;

the established cold section ascending channel model is shown in formulas (31) to (37):

in the formula, ρ_CL,RCIs the density of working medium in the ascending channel of the cold section; w_CL,RCThe flow velocity of working medium in the ascending channel of the cold section; rho_CL,MTThe density of the metal wall of the inverted U-shaped pipe of the cold section; c_P,CL,MTThe constant pressure specific heat capacity of the metal wall of the inverted U-shaped pipe of the cold section; t is_CL,MTThe temperature of the metal wall of the inverted U-shaped pipe of the cold section; k_CL,RC,PRThe heat transfer coefficient between the working medium of the second loop of the preheating area of the ascending channel of the cold section and the metal wall of the inverted U-shaped pipe is determined; d_CL,MTThe inner diameter of the inverted U-shaped pipe of the cold section; t is_CL,RC，PRThe temperature of a liquid phase working medium in a preheating area of a cold section ascending channel; rho_CL,RC，PRThe density of a liquid phase working medium in a preheating area of a cold section ascending channel;

C_P,CL,RC,PRthe constant pressure specific heat capacity of a liquid phase working medium in a preheating area of a cold section ascending channel; w_CL,RC,PRThe flow velocity of the liquid phase working medium in the preheating area of the ascending channel of the cold section; k_CL,RC,BRThe heat transfer coefficient between the working medium of the second loop of the boiling zone of the ascending channel of the cold section and the metal wall of the inverted U-shaped pipe is determined; t is_CL,RC,BRThe temperature of a gas-liquid mixed phase working medium in a boiling area of a cold section ascending channel; rho_CL,RC,BRThe density of a gas-liquid mixed phase working medium in a boiling region of an ascending channel of a cold section; c_P,CL,RC,BRThe constant pressure specific heat capacity of a gas-liquid mixed phase working medium in a boiling region of a cold section ascending channel; w_CL,RC,BRThe flow velocity of a gas-liquid mixed phase working medium in a boiling region of a cold section ascending channel; p_CL,RC,PRThe pressure a of the liquid phase working medium in the preheating area of the ascending channel of the cold section; g_CL,RC,PRMass flow of liquid phase working medium in a preheating area of a cold section ascending channel; f. of_CL,RC,PRIs the friction factor of the preheating zone of the ascending channel of the cold section; d_e,CL,RC,PRThe equivalent diameter of the preheating zone of the ascending channel of the cold section; xi_CL,RC,PRIs the local resistance coefficient of the preheating zone of the ascending channel of the cold section;

P_CL,RC,BRthe pressure of a gas-liquid mixed phase working medium in a boiling area of a cold section ascending channel; g_CL,RC,BRThe mass flow of the working medium in the gas-liquid mixed phase in the boiling region of the ascending channel of the cold section; f. of_CL,RC,BRIs the friction factor of the boiling zone of the ascending channel of the cold section;

D_e,CL,RC,BRthe equivalent diameter of the boiling zone of the ascending channel of the cold section; xi_CL,RC,BRIs the local resistance coefficient of the boiling area of the ascending channel of the cold section;

and solving the rising channel model of the cold section to obtain the flow velocity, temperature, pressure and heat transfer coefficient distribution of the two-loop working medium along the height of the inverted U-shaped pipe at the current moment of the cold section.

9. The method for estimating mass-gas content distribution of a secondary loop working medium of a steam generator according to claim 1, wherein the calculating the mass-gas content distribution of the secondary loop working medium along the height of the inverted U-shaped tube at the current moment comprises:

in the formula, h_BRIs the specific enthalpy of the gas-liquid mixed phase working medium in the boiling region; h is_ssIs the boiling zone saturated steam specific enthalpy; h is_swIs the boiling zone saturated water specific enthalpy; x is the number of_BRIs the mass gas content of the working medium in the boiling area; h is_BR,h_swAnd h_swAnd calculating according to the temperature and the pressure of the gas-liquid mixed phase working medium in the boiling region through a working medium physical property parameter database.

10. The method for estimating mass-gas content distribution of a secondary loop working medium of a steam generator according to claim 1, further comprising: and establishing a steam-water separator model by using the acquired real-time operation data of the steam generator and the flow speed, temperature and pressure of the gas-liquid mixture working medium at the outlet of the top of the ascending channel, and calculating to obtain the temperature, pressure and mass flow of the gas-phase working medium and the liquid-phase working medium at the outlet of the steam-water separator, wherein the liquid-phase working medium at the outlet of the steam-water separator is the inlet recirculation water of the descending channel model.

11. A steam generator two-loop working medium mass gas content distribution estimation system is characterized by comprising:

the data acquisition module is used for acquiring real-time operation data of the steam generator at a given moment;

the descending channel model module is used for establishing a descending channel model by utilizing the acquired real-time operation data of the steam generator to obtain the temperature, the pressure and the mass flow of the liquid phase working medium at the bottom outlet of the descending channel at the current moment;

the heat transfer coefficient calculation module is used for calculating the heat transfer coefficient between the coolant of the primary loop and the metal wall of the inverted U-shaped pipe and the heat transfer coefficient between the metal wall of the inverted U-shaped pipe and the working medium of the secondary loop by using the acquired real-time operation data of the steam generator;

a loop coolant model module, which establishes a loop coolant model by using the acquired real-time operation data of the related measuring points of the steam generator and the acquired heat transfer coefficient between the loop coolant and the inverted U-shaped tube metal wall to acquire the temperature distribution of the inverted U-shaped tube metal wall;

the ascending channel model module is used for establishing an ascending channel model by utilizing the acquired real-time operation data of the steam generator, the heat transfer coefficient between the metal wall of the inverted U-shaped pipe and the two-loop working medium, the temperature distribution of the metal wall of the inverted U-shaped pipe and the temperature, the pressure and the mass flow of the liquid-phase working medium at the outlet of the bottom of the descending channel, and obtaining the flow velocity, the temperature and the pressure distribution of the two-loop working medium along the height of the inverted U-shaped pipe at the current moment by utilizing the temperature, the pressure and the mass flow of the liquid-phase working medium at the outlet of the bottom of the descending channel as input, so as to calculate the mass gas content distribution of the two-loop;

and the steam-water separator model module is used for establishing a steam-water separator model by utilizing the acquired real-time operation data of the steam generator and the flow velocity, temperature and pressure of the gas-liquid mixture working medium at the outlet of the top of the ascending channel, and calculating the temperature, pressure and mass flow of the gas-phase working medium and the liquid-phase working medium at the outlet of the steam-water separator.

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